docs: def _get_service_provider(self):
          """
          **NOTE**: Can be reduced to just one get call once we remove support
          for the service_class spec entry
          Returns:
              class: class for the loaded provider for that vm_spec
              None: if no provider was specified in the vm_spec
          """
          service_class = self._spec.get('service_class', None)
          if service_class is not None:
              warnings.warn(
                  'The service_class key for a domain is deprecated, you should '
                  'change it to service_provider instead'
              )
              service_provider = _resolve_service_class(
                  class_name=service_class,
                  service_providers=self.service_providers,
              )
          else:
              service_provider = self.service_providers.get(
                  self._spec.get('service_provider', None),
                  None,
              )
  
          return service_provider